Pyrolysis of polyacrylonitrile

Burlant, William J.; Parsons, J. L.

doi:10.1002/pol.1956.1202210107

Cited by 225 publications

(41 citation statements)

References 6 publications

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“…The mechanism for colouration is not fully understood. However, the appearance of black colour is believed to be due to the formation of ladder ring structure [28,29].…”

Section: Precursor Stabilizationmentioning

confidence: 98%

A review of heat treatment on polyacrylonitrile fiber

Rahaman

Ismail

Mustafa

2007

Polymer Degradation and Stability

1,232

856

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“…The mechanism for colouration is not fully understood. However, the appearance of black colour is believed to be due to the formation of ladder ring structure [28,29].…”

Section: Precursor Stabilizationmentioning

confidence: 98%

A review of heat treatment on polyacrylonitrile fiber

Rahaman

Ismail

Mustafa

2007

Polymer Degradation and Stability

1,232

856

View full text Add to dashboard Cite

“…This cyclization concept was adopted in modified form by many subsequent workers. Grassie et al, 6 Burlant and Parsons, 7 LaCombe 8 modified Houtz's cyclization scheme to a partially aromatic structure and this has become the most popular reaction scheme currently quoted in many textbooks. 9 This partially aromatic structure is also called a ladder polymer.…”

mentioning

confidence: 99%

Mechanism and Kinetics of Stabilization Reaction of Polyacrylonitrile and Related Copolymers V. The Change in Birefringence of Acrylonitrile/Methacrylic Acid Copolymer Fibers by Heat Treatment under Fixed Length

Kakida

Tashiro

1998

Polym J

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ABSTRACT:Relationships between birefringence change and structural change of the acrylic precursor fibers. made of acrylonitrile/methacrylic acid copolymer during stabilization reaction in air, were investigated to clarify the causes of birefringence change. The birefringence changed from slightly negative to highly positive by heat treatment at 200'C. The wide-angle X-ray pattern did not change essentially, showing apparently no fiber structure change. The IR spectra clarified the remarkable chemical structure change and resultant formation of the fully aromatic cyclised structure, which is considered the cause for increase of birefringence.KEY WORDS Birefringence/ Wide-Angle X-Ray Photograph/ Fourier Transform Infrared Spectroscopy / Acrylic Precursor Fiber / Fully Aromatic Cyclized Structure / Carbon Fiber / Acrylic fibers made of polyacrylonitrile (PAN) containing acidic comonomers like methacrylic acid, itaconic acid and acrylic acid are the most commonly used precursors for carbon fibers because of excellent performance of PAN based carbon fibers. 1 In PAN based carbon fiber production, stabilization is most important, because the physical properties of carbon fibers are affected significantly by the conditions of stabilization. A lot of studies have been reported concerning the stabilization of PAN since 1950. 2 • 3 According to these studies, acrylic fibers are converted into infusible and nonflammable fibers by heating at 200-3000C for about 1 h in an oxidative atmosphere during stabilization. Only the fibers thus stabilized can be heated to carbonization temperatures (1000-2000°C). 4 The mechanism of stabilization reaction has been studied by many workers. Houts 5 postulated a conjugated, fully heteroaromatic cyclic structure to account for changes taking place during degradation, such as coloration, insolubility and flame resistance. This cyclization concept was adopted in modified form by many subsequent workers. Grassie et al.,6 Burlant and Parsons, 7 LaCombe 8 modified Houtz's cyclization scheme to a partially aromatic structure and this has become the most popular reaction scheme currently quoted in many textbooks. 9 This partially aromatic structure is also called a ladder polymer. 2 However, Schurz proposed an azomethine crosslinking reaction to explain the insolubility of stabilized PAN. 10 Berlin et al. 11 and Fester 12 · 13 believe that hydrogen elimination leads to a conjugated polyene with pendant nitrile groups. As above mentioned, cyclization is thought to be a well established scheme, but it is said that there is still no direct evidence for a cyclization mechanism. 2 We have studied the mechanism of stabilization reaction of PAN and related copolymers by means of an t To whom correspondence should be addressed. 474organized combination of isothermal DSC thermogram and FT-IR spectra. 3 · 14 -17 The initiation of the cyclization reaction by the acidic comonomer, the relationship of heat evolution and changes of the chemical structure of the polymer chain, and efficiency of comonomer...

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“…A hypothesis concerning the formation of heteroaromatic cyclic structures was advanced in one of the earliest studies [2] to explain the phenomena that take place when PAN fibres are heated, such as the appearance of color, loss of solubility and noncombustibility. Different versions of this hypothesis have been advanced by many investigators [3][4][5][6].There is now no doubt that cyclization reactions take place in stabilization of the structure of PAN fibres when they are heated in air [7]. In addition to these reactions, intemaolecular cross-linking, dehydrogenation, aromatization, and other reactions also take place [8].…”

mentioning

confidence: 98%

Structural and chemical transformations in thermooxidative stabilization of copolymeric polyacrylonitrile fibres

Калашник¹,

Zlatoustova²,

Rudinskaya³

et al. 1999

Fibre Chem

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The processes that take place during thermooxidative stabilization in copolymeric polyaclylonitrile (PAN) Polyacrylonitrile (PAN) fibres are widely used for fabricating high-strength carbon fibres. Copolymers ofacrylonitrile with itaconic, acrylic, and methacrylic acids, methyl acrylate, acrylamide, and other comonomers are usually used for this purpose. The latter are used in small amounts, usually 1.5-5%, but play a very important role in creating the structure of the carbon fibre [1].PAN carbon fibres are manufactured in several stages. The stage of stabilization of PAN fibres by thermooxidation in air in the 200-300~ temperature range is one of the most important ones. The fibres are converted into nonmelting and noncombustible structures which can undergo carbonization at high temperatures (1000-2000~Many investigators have studied the mechanism of the reactions that take place in stabilization of fibres. A hypothesis concerning the formation of heteroaromatic cyclic structures was advanced in one of the earliest studies [2] to explain the phenomena that take place when PAN fibres are heated, such as the appearance of color, loss of solubility and noncombustibility. Different versions of this hypothesis have been advanced by many investigators [3][4][5][6].There is now no doubt that cyclization reactions take place in stabilization of the structure of PAN fibres when they are heated in air [7]. In addition to these reactions, intemaolecular cross-linking, dehydrogenation, aromatization, and other reactions also take place [8]. However, the ring formation reaction is still the main reaction that stabilizes the structure of PAN fibres due to polymerization ofnitrile groups, which are converted from conjugated structures at the beginning of cyclization into totally aromatic structures as a result of dehydrogenation of the main chain by incorporation of oxygen atoms in the molecule when heated in oxidizing medium [9].In additioff to chemical transfomlations, PAN fibres also shrink [10, l l]. In the given case, shrinkage is undesirable, since it leads to partial loss of orientation of the macrolnolecules of the polymer and worsening of the mechanical properties of the fibre. For this reason, an attempt is made to avoid shrinkage during fabrication of the carbon fibre or drawing is even conducted in oxidation of PAN fibres. Shrinkage of PAN fibres in the oxidation stage consists of two processes: physical, or primary, and chemical, or secondary shrinkage [12,13].The chemical and mechanical transformations that take place during oxidative stabilization of PAN fibres as one of the stages of preparation of these fibres for their conversion into carbon fibres have thus been relatively widely investigated. However, in our opinion, the mechanisms of these processes have not yet been definitively elucidated. In the research discussed All-Russian Scientific-Research Institute of Polymer Fibres, Mytishchi.

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Pyrolysis of polyacrylonitrile

Cited by 225 publications

References 6 publications

A review of heat treatment on polyacrylonitrile fiber

A review of heat treatment on polyacrylonitrile fiber

Mechanism and Kinetics of Stabilization Reaction of Polyacrylonitrile and Related Copolymers V. The Change in Birefringence of Acrylonitrile/Methacrylic Acid Copolymer Fibers by Heat Treatment under Fixed Length

Structural and chemical transformations in thermooxidative stabilization of copolymeric polyacrylonitrile fibres

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